The picture is BIG. Anyway, I don't see any problem here. Everyone looks in character, mostly Phred, Joe, and Greg. I'm actually surprised that Chubb isn't dying yet, considering that thing he's eating is a light saber. You got Viz's face right. Zack's light saber is even correct, as he froze it. I also assume you drew this before Riddle Transfer, as Smiley doesn't have hair here, and Zack now has fire powers that is on his head, rather than ice powers that can freeze earth, and kill people. Overall, this is actually a good crossover. I really like it!